Hip joint orthoses have heretofore been employed by orthopedic professionals for a variety of problems including, Legg Calf Perthes Disease, brittle bone fractures, osteoarthritis, and post-operative therapy for total hip joint replacement. It is well known that hip hinges for casts and orthoses are employed to control abduction and adduction, flexion and extension, and loading of the femur. Most of the known techniques are designed to maintain the femoral head in its correct anatomical location and approximately normal orientation with respect to the acetabulum during the healing process. In most proscribed treatments, the patient is placed in some degree of abduction and the hip orthosis is adjusted to prevent adduction. Caution is taken to prevent adduction because it is known that such motion causes the femoral head to rotate out of its socket, increasing the likelihood of dislocation.
Traditionally, hip orthosis have included means for adjusting the flexion-extension axes of the hip joint while preventing lateral motion. See Rolfes, U.S. Pat. No. 4,481,941.
More recent devices have included two axes of motion arranged at right angles to one another. See Young et al, application GB 2163352A, published Feb. 26, 1986. The Young et al orthopedic hip hinge is equipped with a first flexion-extension axis that can be adjusted for limited motion and a second abduction-adduction axis having an adjustable locking means for setting the abduction at three different angular setting, namely, 0.degree., 15.degree. and 30.degree.. The second axis of Young et al can also provide free abduction when the shoulder pin is removed from the device. However, since adduction is not blocked, there is a chance that dislocation of the joint will occur, resulting in discomfort to the patient and the likelihood of more surgery. Moreover, the limitation of only three angular settings restricts the available positions for post operative treatment.
The Cerebral Palsy Orthosis by Hosmer.RTM. is designed to provide adjustable abduction to 25.degree., with free abduction beyond setting, thereby avoiding the risk of dislocation presented by Young et al. The Post-Op Total Hip Orthotic Joint, also by Hosmer.RTM., has a 45.degree. fixed flexion and abduction axis which can be pre-set to maintain positive medial pressure to the femoral head to prevent accidental dislocation of a prosthesis from the acetabular cup implanted in the ilium. The abduction axis is adjustable to 13.degree. with a small wedge, and to 25.degree. with a large wedge.
None of the prior art devices, however, provides for the gradual shortening of the overall length of the side bars, in conjunction with their hinges, referred hereinafter as "arm assembly", as the femoral head rotates and the distance between the hip and the thigh of the patient decreases with abduction. Since these appliances are relatively rigid along the length of the arm assembly, the shortening of the distance between the hip and the thigh causes sliding of the waist band and/or pistoning of the thigh attachment, resulting in discomfort to the patient. Although, Rolfes and others have provided for adjustments to the length of the control arms, these adjustments are fixed and are merely an accommodation for the height of the patient.
Accordingly, there is a need for an orthopedic hinge for use with hip joints that provides for variable control arm length as the distance between the hip and thigh of a patient decreases during abduction. There is also a need for an orthopedic hip hinge that provides free abduction within a limited range which also provides a greater degree of assimilation of the hip joint.